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			<h1>common_schema</h1> <strong>2.2</strong> documentation
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				<h2><a href="query_script_input.html">query_script_input</a></h2>	

<p>
<strong>input</strong>: declaration and assignment of QueryScript local variables by externally provided values
</p>

<h3>SYNOPSIS</h3>
<p>
<blockquote><pre>input $variable1 [, $variable2 ...];
if ($variable1 = 'x')
{
  statement;
}
</pre></blockquote>
</p>

<h3>DESCRIPTION</h3>
<p> 
<i>input</i> is a QueryScript <a href="query_script_statements.html">statement</a> which declares
<a href="query_script_variables.html">local variables</a>, and assigns them values as given from an
external source.
</p>
<p>
The <i>input</i> statement is only expected to appears once, if at all, within a script.
It must not appear within a loop. The variables declared by <i>input</i> are local variables
as any other variable, and the same rules apply for them as for all local variables. 
</p>

<p>
<i>input</i> makes for an interface between external routines and QueryScript. A routines which
wishes to invoke a script based on some values, passes pre-defined values via MySQL user defined
variables, and these are assigned to the <i>input</i> local variables.
</p>

<p>
In particular, when an <i>input</i> statement is encountered, the following MySQL user defined
variables are looked at:
<ul>
	<li><strong>@_query_script_input_col1</strong>, assigned to 1st declared variable.</li>
	<li><strong>@_query_script_input_col2</strong>, assigned to 2nd declared variable.</li>
	<li>...</li>
	<li><strong>@_query_script_input_col9</strong>, assigned to 9th declared variable.</li>
</ul>
While syntactically permitted, it makes no sense to declare more than <strong>9</strong> input
variables, as nothing will map to any variable exceeding the 9th.
</p>

<p>
To illustrate, consider:
<blockquote><pre>
input $a, $b, $c;
</pre></blockquote>
<br/><strong>$a</strong> will be assigned the value of <strong>@_query_script_input_col1</strong>.
<br/><strong>$b</strong> will be assigned the value of <strong>@_query_script_input_col2</strong>.
<br/><strong>$c</strong> will be assigned the value of <strong>@_query_script_input_col3</strong>.
<br/>The values of <strong>@_query_script_input_col[4..9]</strong> remain unread.
</p>

<p>
A routine which in fact sends input data to QueryScript is <a href="foreach.html">foreach()</a> 
(not to be confused with QueryScript's own <a href="query_script_foreach.html">foreach</a> flow
control looping device). In the following example:
<blockquote><pre>
mysql&gt; call foreach('{USA, FRA, CAN}', '
  input $country;
  DELETE FROM world.City WHERE CountryCode = $country;
');
</pre></blockquote>
<i>foreach</i> sets <strong>@_query_script_input_col1</strong> to the iterating 
value of 'USA', 'FRA', 'CAN', each in turn, and calls upon the script which assigns the value
onto the <strong>$country</strong> variable.
</p>

<p>
For completeness, the above example is very simple, so as to illustrate the workings of <i>input</i>.
The following two code fragments perform the same operation as the above:
<blockquote><pre>
mysql&gt; call foreach('{USA, FRA, CAN}', 'DELETE FROM world.City WHERE CountryCode = ''${1}''');
</pre></blockquote>
Or, via QueryScript only:
<blockquote><pre>
foreach($country: {USA, FRA, CAN})
{
  DELETE FROM world.City WHERE CountryCode = $country;
}
</pre></blockquote>

<p>
Developers who wish to integrate QueryScript execution into their code are able to do so
by providing the aforementioned user defined variables and by using <i>input</i>.
</p>

<h3>SEE ALSO</h3>
<a href="query_script_var.html">var</a>,
<a href="query_script_variables.html">Variables</a>

<h3>AUTHOR</h3>
Shlomi Noach


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